Looking at buying a TD 3ltr surf and building her into a beast, how many km's do they go to until they ***** themselves and what parts should i look a replacing after buying it, also any other things people wanna throw out there for me as well. Everything will be appreciated!

Mitch
if you fit an intercooler it will help the engine by giving cooler air to the intake and possibly lower EGT levels a bit.
If you have a bonnet scoop it may give the IC some air but it may begin to pressurize the engine bay and since the engine water cooling airflow is through the radiator, the scoop pressure might reduce the cooling through the radiator a bit and cause overheating.
It's sometimes a fine balance of scoop flow and air through rad flow so all works well. You may have to add an underbody air deflector to cause a partial vacuum below the engine bay so flow is restored through the engine bay. It's a bit hard to tell what flows will happen and often a bit of trial and error has to be done. In the factory it's called R&D.